The function of a cell, tissue, or organism is dependent upon the coordinate interplay of myriad processes. This interplay involves intra- and extracellular signaling or communication. "Signal transduction" is a generic term used to describe diverse processes involved in intra- and extra-cellular communication. In essence, signal transduction entails the mechanisms whereby a cell receives an internal or external stimulus/message and activates/inactivates effectors whose engagement result in a perturbation of cellular homeostasis. Thus, the phenotype, characteristics and function of a cell/organism are highly dependent upon signal transduction processes. Signal transduction research is very germane to the field of toxicology because many toxicants disrupt the coordinate interplay of signaling pathways. They do so by modulating the production of "second messenger? molecules or the activities of signaling effectors. Knowledge of signaling networks, their interplay with one another, and the biological processes they affect is useful in predicting and defining both mode of action, and consequences of toxicant exposure. Such knowledge is also useful in defining strategies to modulate the consequences of toxicant exposure, and the subsequent development of acute illness/injury or disease. The overall mission of the Cell Signaling & Function (CSF) Research Core is to encourage and facilitate the interaction and collaboration of Center scientists who have interests in understanding the mediators, modulators and mechanisms of signal transduction in toxicant-perturbed, normal, and neoplastic cells and tissues, and to relate these signaling processes to cellular function and ultimately to human health. The broad based goals of the CSF Research core are to: 1) maintain a functional, interactive group of scientists who have interests in signal transduction research, 2) provide a focus for research interactions (i.e., collaborations) on topics involving toxicants, signaling and cell function, with emphasis on those that affect human health, 3) develop and maintain a contemporary intellectual and technical expertise that is a resource to Center members and other University investigators; and 4) facilitate the translation of mechanistic "bench" research and insights into application toward human populations through intra- and inter-programmatic interactions and collaborations.